U.S. Pat. No. 6,974,048 discloses a torque converter with dual clutches operated by a common piston. Unfortunately, this patent refers to clutches that control torque between a front cover and a pump or bypass clutch, which is not applicable to clutches for operating a torque converter having forward and reverse stator and a turbine. Also unfortunately, the clutches are balanced in an application where the piston is not mounted in the front cover; thus high axial forces would have to be resolved. Further, this system uses a spring applied clutch, which would not function well in a clutch system for a converter with forward and reverse stators. For example, on start up one clutch would be applied and start pulling. With the spring applied system it would be difficult to control a neutral state in with neither clutch is applied. Specifically, the control oil pressure cavity 12 would have to offset partial spring force as well as changing charge pressure.
Unfortunately, oil pressure must be the highest in converter bypass mode because pressure in the clutch chamber must overcome charge pressure-before the clutch can start transmitting torque. Then, the effective clutch pressure is the difference between charge and clutch apply pressure. This high pressure must be present in converter bypass mode at highway speeds and would adversely affect gas mileage.
Unfortunately, there is no torque interrupt state in the patent. Clutch “PK” is applied first, then sequentially clutch “WK” is applied, which is desirable for the application described in the patent as it would not be desirable to have a torque interrupt when applying the by-pass clutch.
Thus, there is a long-felt need for balanced clutch assembly for a torque converter with forward and reverse stators having minimal axial space requirements and a simplified fluid control system.